The present invention relates to a connection ring as well as an arrangement and a method for use in connecting duct elements. The invention concerns in particular, but not exclusively, connection of ventilation duct elements having an oval cross-section.
A known system of connecting ventilation duct elements is disclosed in a pamphlet entitled xe2x80x9cRound and Oval Duct Connection Systemxe2x80x9d and issued in 1998 by the US company Accu Flange Mfg. On the first two pages of this pamphlet, it is shown how the AccuFlange system works, for both round and oval ventilation ducts.
First, each of the two ducts to be connected is provided with a flanged coupling ring at its open end. Normally, sealing means is provided in order to secure tight joints between the coupling ring and the duct. Often, a sealing mastic is applied on the inside of the duct. Second, the two ducts are aligned end-to-end and the flanges of the coupling rings are abutted and connected to each other by means of fastening screws driven through the flanges. This fastening is shown in detail in a figure under the subtitle xe2x80x9cTechnical Dataxe2x80x9d in the AccuFlange pamphlet, and the duct connection is schematically shown in the section xe2x80x9cSubmittal Summaryxe2x80x9d.
The AccuFlange system has, however, certain drawbacks. When mounting ducts in situ and along the ceiling, at the junction with the wall, the aim is that the ducts should be located as close to the ceiling and the wall as possible. Thus, when mounting AccuFlange ducts in situ at such locations, it is hard for the assembly personnel to find room for driving the fastening screws into the abutting flanges. Due to this cumbersome fastening operation, it is quite common that too few screws are driven through the portions of the flange that are facing the ceiling and the wall. This inadequate connection of the ducts may lead to air leakage in the joint between them.
A further disadvantage of the AccuFlange system is that the coupling ring flange is weakened in the areas where the fastening screws are driven through the material.
In general terms, the AccuFlange ducts are complicated to handle due to several operations when connecting the flanged coupling rings to the open ends of the ducts and also due to the specific difficulties when mounting the ducts near the ceiling.
U.S. Pat. No. 5,983,496 to Hermanson (corresponding to British Patent No. 2,311,031) discloses how an AccuFlange coupling ring is manufactured and used. As shown in FIGS. 5 and 5A, the coupling ring is built up of four separate parts, namely two straight parts and two semi-circular parts. The ends of the straight parts are connected to the ends of the semi-circular parts by welding (col. 10, lines 33-36). The flange of the coupling ring shown in FIGS. 1-4 is formed by a special operation called spin forming which is fairly hard to handle in practice. In FIG. 4, the above-mentioned fastening by means of screws is shown.
It is nowadays felt that there is a need for a duct connecting system which is simpler to mount and which has coupling rings that are simpler to handle and manufacture.
As to known arrangements for connecting duct elements, mention should also be made of Applicant""s system called xe2x80x9cLindabRektxe2x80x9d. In written instructions for assembling of LindabRekt, distributed in 1998, it is shown how duct elements having a rectangular cross-section are connected by means of a special frame structure that is mounted on the open end of the duct. This frame structure comprises four separate parts LS1 that are fitted on the four end rim portions of a rectangular duct. The ducts are aligned end-to-end with the respective frame structures abutting each other, and special rails LS3 are fitted on the frame parts LS1 for connecting the two ducts together.
The LindabRekt frame structure LS3 is, however, not to be compared with a coupling ring of the type discussed above, since it consists of several separate parts which are separately fitted on the end rim of the ducts.
As to prior art, still another reference may be mentioned, namely a document entitled xe2x80x9cHVAC Duct Contruction Standards Metal and Flexiblexe2x80x9d, second edition, issued by SMACNA (the first edition of which is cited in Hermanson""s U.S. Pat. No. 5,983,496). In sections 1.8 and 1.9 of this SMACNA document, various joint reinforcement and sealing techniques are discussed in relation to rectangular ducts. However, no duct coupling concept by which the above drawbacks of prior art are eliminated, is presented in the SMACNA reference.
The main object of the present invention is to eliminate, at least partially, the disadvantages of prior art systems and to provide an improved concept for coupling duct elements of this kind.
A particular object of the invention is to provide a new coupling ring which is easy to manufacture and easy to mount on the duct.
Still another object of the invention is to provide an improved technique for connecting duct elements by means of a new connecting arrangement and a new connecting method.
These and further objects which will appear from the specification to follow, have now been achieved by a flanged coupling ring for a duct element having a connection portion, the coupling ring comprising:
a mounting section having a periphery and being configured to be mounted on the connection portion of the duct element; and
flange means having a periphery and extending outwards from the periphery of the mounting section;
the flange means comprising, along its periphery, flanged coupling portions for connecting two duct elements together, each of which is provided with a coupling ring, by means of external coupling means configured to engage with the flanged coupling portions.
The objects are also achieved by an arrangement for connecting a first duct element to a second duct element, each of the duct elements having a connection portion, the arrangement comprising:
a first flanged coupling ring with a mounting section having a periphery and being configured to be mounted on the connection portion of the first duct element;
a second flanged coupling ring with a mounting section having a periphery and being configured to be mounted on the connection portion of the second duct element;
each of the coupling rings comprising flange means having a periphery and extending outwards from the periphery of the mounting section, the flange means of the coupling rings comprising, along a periphery thereof, flanged coupling portions for connecting the duct elements; and
external coupling means configured to engage with the flanged coupling portions of the flange means of the coupling rings, when the flanged coupling portions are abutted, in order to provide the connection of the duct elements.
Furthermore, the objects are achieved by a method of connecting a first duct element to a second duct element, each of the duct elements having a connection portion provided with a flanged coupling ring with outwardly projecting flange means, the method comprising the steps of:
aligning the connection portions of the two duct elements so that the coupling rings are opposite each other;
abutting the coupling rings so that flanged coupling portions along the periphery of the flange means of the coupling rings are in abutment with each other, thereby forming joint portions; and
bringing external coupling means into mutual engagement with the abutting flanged coupling portions so that the duct elements are connected to each other at the joint portions.
The objects are also achieved by a method, in which the flanged coupling rings are pre-mounted on the duct elements and the duct elements are aligned and abutted as defined above, followed by the step of bringing external coupling means into mutual engagement with the abutting flanged coupling portions.
Thus, the flange means of each coupling ring comprises, along its periphery, flanged coupling portions for connecting two coupling rings together by means of external coupling means, preferably elongate strips or rails, configured to engage with the flanged coupling portions, whereby two duct elements, each provided with coupling rings, are connected. This is a very favorable structure, as will be discussed further below.
The inventive duct coupling concept has several advantages over prior art. The coupling ring is easy to manufacture, for instance by roll forming operations, and it is also easy to mount the same to the duct element. Preferably, the coupling ring is formed in one piece which emphasizes the simplicity by which it is manufactured. If the flanged coupling portions of the coupling ring are formed as substantially straight portions along the periphery of the flange means, it is easy to fit the external coupling means on the flanged portions.
Most preferably, the external coupling means are elongate strips which are slid onto the straight flanged coupling portions, in a direction which follows the periphery of the flange means. With this structure, no fastening screws have to be driven through the flange means at locations which are difficult to reach, for instance near the ceiling and the wall.
In a preferred embodiment, the flanged coupling portions of the coupling ring are spaced with respect to the periphery of the flange means, and most preferably at least two of the flanged coupling portions are opposite each other with respect to a center axis of the mounting section of the coupling ring. This structure is particularly suitable for oval duct elements, since secure flange connection is provided on each straight portion of the oval joint. Thus, a tight connection is achieved.
In still another preferred embodiment, the mounting section of the coupling ring is an insertion section configured to be inserted in the connection portion of the duct element. It is preferred that the insertion section is provided with an external, circumferential sealing element. As a result, a simple and reliable sealing effect is achieved at the joint between the outside surface of the coupling ring and the inside surface of the duct element. No sealing mastic, as is used in connection with the known AccuFlange system, is needed.
The coupling arrangement or kit itself and the associated method also have many advantages. Two flanged coupling rings, which in the preferred embodiment are similar and formed as unitary pieces, are easily mounted on the connection portions of the duct elements. With the flanged coupling portions of the two duct elements abutting each other, an external coupling means of simple structure is engaged with the flanged coupling portions, and the duct connection is established. In particular when the external coupling means, according to a preferred embodiment, are slidable on the flanged coupling portions, it is very easy to provide the duct connection. Practical tests of a coupling arrangement of this embodiment have shown extremely good results. The time for assemblying two ducts in accordance with the invention is about half of the time required by prior-art arrangements.
It should be mentioned that the invention does not only concern connection of ventilation duct elements, but also connection of other fluid-conducting duct elements, such as ducts for transportation of grain, dust and the like by means of an air flow. Further, it is pointed out that the invention is not restricted to duct elements having a particular cross-section, but the inventive concept is applicable to various cross-sections, including oval, circular, polygonal, etc. Indeed, the invention is particularly advantageous when applied to ducts having an oval cross-section, or a so-called flat-oval cross-section. By this term is meant a cross-sectional shape comprising two straight, parallel, spaced portions and two spaced, semi-circular portions.